849 FXUS63 KMKX 060402 AFDMKX Area Forecast Discussion National Weather Service Milwaukee/Sullivan WI 1002 PM CST Fri Jan 5 2024 .KEY MESSAGES... - Light accumulating snow expected for Saturday. - Strong low pressure to track south and east of Lake MI Tue- Wed. Accumulating snow possible Mon nt-Tue nt, but also rain for far se WI and near the lake. && .UPDATE... Issued 1000 PM CST Fri Jan 5 2024 The previous forecast issuance remains on track for Saturday. IR Satellite continues to show plenty of clouds overhead and upstream, with no radar returns below 5,000 feet. The clouds will continue to thicken and descend tonight, gradually overcoming the dry air beneath them and producing light snow. Forecast soundings continue to show snow chances reaching far southeastern WI by 09z tonight, then spreading northward. High- res models currently place the highest snow chances (60 to 90%) east of a line from Beloit to Madison to Fond Du Lac in the late morning hours, as a light southeasterly surface wind allows lake effect enhancement. However, the lake effect will also increase surface wet bulb temperatures, limiting accumulations. Best estimate for snow accums is still around an inch for the lakeshore counties and towards the Kettle Moraine, tapering down to around 0.5 inches in Madison. Sheppard && .SHORT TERM... Issued 325 PM CST Fri Jan 5 2024 Tonight through Saturday night: Clouds will continue to stream toward srn WI from the south this afternoon. Chances for lgt snow will then increase after 09Z tnt for se WI as the upper wave over KS approaches. A 100-120 kt sly jet streak on the east side of the upper low over KS will lift the upper wave through srn WI on Sat and becoming negative tilt as it does so. 850-700 mb warm advection will increase over ern WI and combine with PVA and WAA at the jet level to maximize lift and qpf over ern WI. A sely boundary layer flow and lake to 850 mb temp differences of 11-13C will contribute to lake enhanced snow for the lake counties, although sfc temps above freezing will limit the snow accum. Overall qpf of 0.15-0.20 inches for the lake counties decreasing to less than 0.05 inches toward Madison. Expected snow accums around an inch for the lake counties and Washington and Waukesha Counties, then decreasing to less than one half inch toward Madison. Another shortwave trough will follow for Sat nt-Sun AM but will be weak with perhaps some flurries. 500 mb height rises will then take hold for Sun PM into Mon ahead of a strong shortwave trough digging from the Pacific NW to the srn Great Plains. Relatively mild temps will continue into Mon. Gehring && .LONG TERM... Issued 325 PM CST Fri Jan 5 2024 Monday night through Friday: The GEFS and ECMWF MSLP ensemble means actually agree fairly well with strong cyclogenesis from OK to the lower Great Lakes from 00Z Tue to 12Z Wed. The system does go negative tilt and occludes as it passes to the east Tue nt. The heavier qpf therefore remains over far se WI but pcpn type would be a rain/snow mix for much of the lake counties. Will continue to message snow potential but pcpn type challenges and any shifts to the north or south. A progressive pattern will continue with the passage of a shortwave trough Wed nt then another upper wave and low pressure area passing through the Ohio Valley next weekend. 30-40 percent chances for snow is thus forecast Wed nt-Fri with cooling temperatures. Gehring && .AVIATION... Issued 1000 PM CST Fri Jan 5 2024 Clouds bases will continue to descend overnight, bringing widespread MVFR conditions, and eventually Fuel Alt and IFR conditions Saturday. Snow is expected to gradually onset tonight (particularly after 0900 UTC), ramp up late Saturday morning, then gradually taper off Saturday afternoon. Most of the snow will fall in eastern / lakeshore counties, but due to temps slightly above freezing, only around an inch of accumulation is expected at this time. That said, the falling snow could limit visibility to around 1 SM at times. Areas further west (towards KMSN) are expected to observe slower snow rates and even lower accumulations. Winds remain fairly calm throughout the TAF period. Sheppard && .MARINE... Issued 325 PM CST Fri Jan 5 2024 High pressure of 30.3 inches from Ohio to the East Coast will remain there into this evening, while weak low pressure over the northern Great Plains moves to Lake Superior by Saturday night. Another weak low will move into southern Lake Michigan from the south for Saturday afternoon and evening, then moving east. Light southerly winds tonight followed by modest southeast winds for Saturday. Modest west to northwesterly winds will then develop Saturday night over southern Lake Michigan then expanding to the north for Sunday as weak low pressure moves to the east. A strong low pressure system is then expected to track just south and east of Lake Michigan for Tuesday into Wednesday. Brisk east winds will back northerly during this time. Depending on the strength of the low pressure area, gales could develop. Gehring && .MKX WATCHES/WARNINGS/ADVISORIES... WI...None. LM...None. && $$ Visit us at weather.gov/milwaukee Follow us on Facebook, Twitter, and YouTube at: www.facebook.com/NWSMilwaukee www.twitter.com/NWSMilwaukee www.youtube.com/NWSMilwaukee